Exam II | CNS Flashcards
What are spinal enlargements?
widening of the cord in cervical and lumbar regions due to additional wiring to the upper and lower limbs, respectively
How does the ratio of white to gray matter change down the length of the cord?
the ratio decreases (there is less white matter compared to gray matter), with the exception of the thoracic region
What cells line the central canal, and how does it change over time?
- ependymal cells
- becomes occluded with age
What is the conus medullaris, and where does it end?
- the end of the spinal cord
- ends between L1 and L2
What are 2 structural modifications of the pia mater?
- filum terminale
- denticulate ligament
What is the filum terminale, and what is its significance?
- a filamentous extension of the pia mater from the medullary cone to the coccyx
- it has no neural function
What is the function of the denticulate ligament?
-helps to hold white matter of cord in place relative to the dura mater
What is the cauda equina composed of?
- a bundle of spinal nerves and spinal nerve rootlets
- contains nerve pairs L2-L5, S1-S5, and the coccygeal nerve
How do the roots of the cord change along the cord length?
the roots lengthen, to accommodate the cauda equina
How can you tell the difference between dorsal and ventral horns?
dorsal horns extend to the edge
What is the level of termination of the cervical cord?
C7
What is the level of termination of the thoracic cord?
stops before T12
What is the level of termination of the lumbar cord?
stops before L1
Where is the sacral region of the cord?
L1
What is the epidural space?
The space between dura mater and vertebral wall. It is superficial to dura mater
At what level is an epidural or LP done? What is the difference between the two?
- always below the cord (below L1)
- LP penetrates dura mater to extract CSF from subarachnoid space. Sometimes done in sacral region
- epidural injects anesthetic superficial to dura mater, in epidural space
How long is the typical spinal cord?
less than 20” long
Where is the superior sagittal sinus, and what does it contain?
- a dural compartment between dura and arachnoid mater
- contains low pressure venous blood
Where is the subarachnoid located, and what fluid does it contain?
- Between the pia mater and the arachnoid mater
- contains CSF
Arachnoid villi structure, function, and location
- herniations of the arachnoid membrane that penetrate the overlying dura and invaginate through the walls of the cranial dural sinuses
- return CSF to venous blood of cranial sinus, esp. superior sagittal sinus
what is the choroid plexus?
- a tissue in the ventricles of the brain that produces CSF from blood
- creates a positive pressure to facilitate flow back into subarachnoid space
- also clears out amyloid and other misfolded proteins
CSF circulation
- leaves cranial sinus of choroid plexus
- circulates downward form lateral ventricles into 3rd and 4th ventricles
- then around (subarachnoid space) and through (central canal) the spinal cord
- and around entire brain
- pressure drives CSF in arachnoid space through arachnoid villi and back into the venous blood of cranial sinuses
What makes up the white columns of the spinal cord?
posterior, lateral, and anterior funiculus
what branches off the spinal nerve?
- dorsal ramus
- ventral ramus
- grey and white rami communicantes
What connects spinal nerve to sympathetic chain?
gray and white rami communicantes
What nerves does the dorsal ramus have? The ventral ramus? Explain.
- both have mixed nerves
- dorsal ramus has longer branches (tend to be sensory, reach cutaneous layer) and shorter branches (are motor, reach erector spinae muscles)
- ventral ramus also has cutaneous branches which are sensory
Which rami form nerve plexuses?
ventral rami of C1-T1 and L1-S4
incomplete SCI
at least partial sensory OR motor function is retained below the site of injury
complete SCI
total loss of sensory AND motor function below site of injury (both sides effected equally)
What are the complications of SCI?
- bowel/ bladder dysfunction
- respiratory and heart problems
- chronic pain
What fraction of SCI patients require ventilatory assistance?
1/3
Paraplegia
- results from injuries lower on the spine
- affects parts of trunk, pelvic region, and legs
Quadriplegia
- results from injuries higher on the spine
- affects trunk, arms, legs, hands, and pelvic region
hemiplegia
complete loss of sensorimotor function one one side of the body
What are common therapies for SCI?
- steroid therapy helpful if administered early
- rehab
- physical therapy
- electrical stimulation
What determines amount of sensorimotor loss of SCI?
- level of injury
- laterality of injury
What are the characteristics of the dura mater?
- tough
- fibrous
- densely infused with nociceptors
What are the 2 layers of the dura mater?
- periosteal
- meningeal
- sperate at the superior sagittal sinus
What is the tentorium cerebelli?
a portion of the dura mater that separates the cerebrum from the cerebellum
What is the falx cerebri?
- a portion of the dura mater that separates the two cerebral hemispheres
- made up of dural meningeal layer
What are the characteristics of the arachnoid mater?
- thin
- extensively vascularized
- with arachnoid processes extending toward pia
- subarachnoid space filled with CSF
What are the characteristics of the pia mater?
- very thin, delicate
- tightly bound to surface of brain and blood vessels
What causes meningitis?
viral, bacterial, or fungal infection of CNS or meninges
What form of meningitis is most severe?
bacterial
What bacteria cause meningitis?
haemophilis, pneumococcus, and meningococcus
What are the symptoms of meningitis?
- HA
- high fever
- altered mental status
- phonophobia and photophobia
- nuchal rigidity
- petechiae in trunk, membranes, and extremities (if meningococcal)
blood composition changes in response to what?
- diet
- exercise
- stress
BBB function
- ensures brain receives correct mixture of nutrients (since CNS is not able to handle large variations in blood composition)
- allows passage of water, some molecules, and small proteins
- removes potential toxins
What is levadopa?
- a dopamine precursor used in the management of Parkinson’s disease
- dopamine cannot cross BBB
What acts as an intermediary between blood and neurons in the BBB?
- specialized capillaries with endothelial cells made up tight and gap junctions
- membrane transporters
- astrocytes
What type of transport allows for transfer of nutrients and wastes in BBB?
- simple diffusion
- facilitated diffusion
- active transport
What characteristics do drugs need to have to be able to pass BBB?
- a high partition coefficient (lipophilicity and size smaller than 500 Da)
- evasion of active extrusion (from video)
What would happen if arachnoid villi were not functioning properly?
hydrocephalus
What connects third and 4th ventricle?
cerebral aqueduct of midbrain
what joins the lateral ventricles?
intraventricular foramen
What does the 4th ventricle give rise to inferiorly?
the central canal
How much CSF do the ventricles contain?
40 mL
How much CSF does the entire CNS contain?
150 mL
How much CSF is produced in the body each day?
500 mL
How does CSF composition compare to that of blood?
- more acidic
- lower concentration of K+ and Ca2+
- no RBCs, smaller number of WBCs
- smaller amount of proteins, lipids, hormones, microRNAs, cholesterol, & metabolites
What is the difference between diploic and emissary veins?
- diploic veins extend through middle portion of cranial bone into interior
- emissary bones extend from skull surface to interior
What can cause nasal CSF drainage?
pathology, trauma, or genetic disorder of the sphenoid bone
How much CSF is turned over each day?
0.5L (same as amount produced each day)
What are the functions of CSF?
- provides appropriate environment for neurons and nutrients
- provides buoyant medium for brain, providing hydraulic protection against physical trauma
Choroid cell function
- monitor CSF compositions
- regulate admission of immune cells, ions, and some proteins in the brain
Choroid plexus atrophy is seen in what ailments?
- Alzheimer’s dz
- CVA
- MS
- psychiatric diseases
Choroid plexus atrophy leads to what?
reduced clearance of amyloids and misfolded proteins
primary cilium is found in what kind of cells?
- metabolically active cells
- most epithelial cells
- most neurons
- choroid cells
- ependymocytes
Glymphatic system function
contribute to nightly clearance of metabolic wastes from the brain during sleep
What does the glymphatic system require to function?
an efficient choroid and astrocytes to regulate flow of blood and CSF through the ECF
What connects the flow of CSF from the pararterial areas to the paravenous areas in the glymphatic system?
the brain parenchyma
What may happen to neurons while you sleep?
they may shrink up to 40% in order to facilitate flow of cleansing fluids and removal of waste products
What percent of wastes may be removed by the glymphatic system?
up to 80% of protein waste and other metabolites
Where is the brainstem located?
between cerebrum and spinal cord
Where is the pineal gland located?
behind the brainstem
What is a brainstem patient?
patient is breathing and with heartbeat but cerebrum no longer functionally attached to brainstem
How can you tell what view of the brainstem you are looking at?
the anterior of the pons is protruding
What is decussation?
- the point at which the fibers cross the midline
- this is what allows your left brain to control your right limbs and vice versa
Where does motor decussation occur?
at the anterior medulla, at the pyramidal tracts
what is the medial lemniscus made of?
cuneate and gracile fasciculus
Where does sensory decussation occur?
at the medial lemniscus of posterior medulla
What cranial nerves are on the medulla?
X, XI, & XII
What are the medullary vital centers?
- cardiac center: regulates HR and stoke volume
- vasomotor center: regulates vasomotor tone
- respiratory center: with pons, regulates rhythm, rate, & depth of breathing
What do the medullary nuclei do? Name them.
work in concert with ANS to regulate BP, HR, and RR.
- nucleus cuneatus
- nucleus gracilis
- olivary nucleus
______ arteries converge at the medulla.
vertebral
What is the largest part of the brainstem?
the pons
What is the adjective for pons?
pontine
What cranial nerves extend from pons nuclei?
V, VI, VII & VIII
What is anterior to the pons?
4th ventricle
What are the respiratory centers, and where are they located?
located in the pons
- pneumotaxic center
- apnesustic center
superior colliculi are located where and responsible for what?
- located in midbrain
- responsible for reflex movements of eyes, head, and neck for visual stimuli
What are the cerebral peduncles?
- descending pyramidal tracts to cerebellum from the midbrain
- made of white matter
what is the substantia nigra?
- dopaminergic part of basal nuclei
- dark due to neuromelanin
- plays critical role in movement, reward, & addiction
What causes Parkinson’s disease?
loss of dopamine in SNpc (nigrostriatal pathway)
Describe the red nuclei of the midbrain.
- has blood vessels
- is a motor tract. regulates posture & muscle tone
inferior colliculi are located where and responsible for what?
- located in the midbrain
- responsible for reflex movements of head, neck, and trunk from auditory stimuli
What cranial nerve nucleus does the midbrain have?
oculomotor nucleus
What is reticular formation, and where is it located?
- scattered throughout brainstem
- involved in vigilance, consciousness, arousal
- serotonergic elements affect mood, habituation
What is habituation?
occurs when animals are exposed to the same stimuli repeatedly, and eventually stop responding to that stimulus
Location of hypothalamus
- anterior and somewhat inferior to thalamus
- superior to pituitary
- anterior to midbrain
What is the diencephalon made up of?
mostly of thalamus. there’s also hypothalamus, epithalamus, and subthalamus
what are the 4 types of hypothalamic nuclei?
- mamillary region
- tuberal region
- supraoptic region
- preoptic region
What does the hypothalamus regulate?
- endocrine and ANS
- hunger, satiety, thirst
- body temperature
- aspects of sleep and fatigue
- behaviors (e.g. parenting, bonding)
- part of the limbic system (basic drives, emotions, bodily responses to emotion)
thalamus location
- just above brainstem
- adjacent to third ventricle
What is thalamocortical chatter?
interactions between thalamus and mostly sensory regions of cerebral cortex
All sensory information (except olfactory, are conveyed directly to what nuclei?
thalamic nuclei
- medial geniculate
- lateral geniculate
- ventral posterior
- ventral anterior
What is the difference between lateral geniculate and medial geniculate nuclei?
- lateral receives retinal signals
- medial receives auditory inputs
The thalamus has extensive interconnections with what two structures?
- cerebral cortex (mostly sensory regions)
- basal nuclei
How does the thalamus process complex sensory info?
filters, prioritizes, evaluates, then sends signals to other regions of the brain for further analysis
What sensations are conveyed to thalamus via the spinothalamic tract?
- pain
- temperature
- crude touch
Importance of thalamus
- initial integration/processing of sensory info
- contributes to vigilance and alertness
- hippocampal circuits suggest role in memory
What 2 brain structures play a role in vigilance?
- thalamus
- reticular formation of midbrain
Where is the ventral posterior nuclei located, and where does the relay information?
- thalamus
- to somatosensory cortex
Where is the ventral anterior nuclei located, and where does the relay information?
- thalamus
- to prefrontal cortex
Cerebellum location
posterior to pons and 4th ventricle
How does the cerebellum compare to the cerebrum in cellular composition?
has 3 more cells than cerebellum
cerebellum function
- allows for precisely timed and coordinated movements, and motor learning
- uses sensory info to rapidly correct motor signals
What is a peduncle, and what are the 3 cerebellar peduncles?
-a white matter pathway
superior, middle, and inferior cerebellar peduncles
What is meant by calling the cerebellum an analytical comparator?
it uses sensory info to rapidly correct motor signals, ensuring that actual movements correspond to intentions
What side to cerebellar efferents control?
the same side; they’re ipsilateral
cerebellar patients often have what characteristics?
- moving slowly or awkwardly
- falling
What is asynergia?
impaired coordination
What is dysmetria?
inability to estimate distances
unfolding the cerebellum would produce a sheet how long?
1 meter
What is adiadochokinesia?
inability to make rapid, repetitive movements
What is an intention tremor?
involuntary, rhythmic muscle contractions (oscillations) that occur during a purposeful, voluntary movement
Cerebellar ataxia is characterized as what?
wide foot movements when walking
What is hypotonia?
weak, flaccid muscles
What are the cells of the cerebellum?
- Purkinje cells
- Golgi cells
- Basket Cell
- Granule cell
- stellate cells
- Mossy fibers
- climbing fibers
cerebellum structure
- molecular layer (superficial)
- granular layer (deep)
- Purkinje cells between these two layers send large axons to the inner white matter and deep cerebellar nuclei
- White matter branching termed arbor vitae
Purkinje cells
- dendrites extend into molecular layer of cerebellum
- axons extend to the inner white matter and deep cerebellar nuclei
- are GABAergic
What are basal nuclei?
- Regions of gray matter located within myelinated white matter covering the brain
- extend from midbrain to adjacent of lateral ventricles
- essential for normal, voluntary movement
What are the components of the basal nuclei?
- lentiform nucleus (putamen and globus pallidus)
- caudate
- previous two make up the striatum
- nucleus accumbens
- SNpc
What is the striatum, and what basal nuclei components does it contain?
- superior portion of nigrostriatal pathway
- dopaminergic and glutamatergic
- has lentiform nucleus globus pallidus and caudate)
What 3 regions of the brain are responsible for motor function?
- cerebellum
- motor cortex
- basal nuclei
Damage to the striatum is responsible for what disease?
Huntington’s
Insult to basal nuclei can lead to what ailments?
- Huntington’s dz
- Parkinson’s dz
- OCD
- Tourette’s
- hemiballismus
What is meant by calling the basal nuclei a filtration system?
“selects” correct motor sequence for the desired outcome and acts to inhibit or constrain gross movements
basal nuclei function
- essential for normal, voluntary movement
- learning of motor “routines” (e.g. tying shoe, playing instrument, driving car)
- possibly emotions and other aspects of learning
What are the symptoms of Parkinson’s disease?
- impaired voluntary movement
- tremors
- exaggerated movement
- freezing
What is the general confirmation of the hippocampus?
C-shaped structure in medial temporal lobe, posterior to amygdala
Damage to the hippocampus leads to what?
memory impairment
What tends to decrease hippocampal size?
depression
Hippocampus function
- essential for memory formation
- esp. important for learning of location and time relationships (e.g. navigation)
- place cells and grid cells enable animals to construct mental maps of their surroundings
- part of the limbic system which plays a role in emotions
How does something become long term memory?
- after immediate sensory data is temporarily transcribed by neurons in the cortex, it gets sent to the hippocampus where special proteins work to strengthen cortical synaptic connections
- if the experience was strong enough or we remember it periodically for the first few days, the hippocampus transfers the memory back to the cortex for permanent storage
What is the difference between memory formation in the basal ganglia and cerebellum and memory formation in the hippocampus?
- hippocampus has declarative memory (name, dates, and facts)
- cerebellum and basal nuclei control procedural memory (signing your name, riding a bike)
